Blade cleaners have been used extensively in electrostatographic copiers and printers as a method of removing untransferred toner particles, carrier particles and other foreign matter such as paper dust, lint and fibers from the surface of an organic or inorganic photoconductor drum or a web.
Blade cleaners have also been applied with other type of cleaners such as magnetic brush and conductive brush cleaners as a method to remove contaminants from a detone roller. Detone rollers are used to remove contaminants from the brushes. In these applications, the cleaning blade does not contact the photosensitive surface. There are still other applications requiring a blade in contact with the surface to be cleaned in which such contact occurs downstream of brush cleaning methods.
Blade cleaners have also been applied to clean other surfaces which are not photosensitive such as an intermediate transfer roller or web, transfer rollers and transport webs in process color copiers or printers.
Cleaning blades come in either scraper or wiper configuration as illustrated in FIGS. 1 and 2. The scraper blade 1 is the most widely used configuration and it is mounted to make an inclination angle, .alpha., of 10.degree. to 35.degree. with a tangent line passing through the contact point as shown in FIG. 1. The wiper blade 2 is mounted to make an inclination angle .beta. of 60.degree. to 85.degree. as shown in FIG. 2.
Cleaning blades are mounted with some engagement or interference "d" of its free end with the surface to be cleaned with sufficient force to enable cleaning. The cleaning blade force is usually within a range of 10 to 80 g/cm, wherein "cm" represents length in centimeters in the cross-track direction. In FIGS. 1 and 2, the blades are shown in the undeformed shape.
Polyurethane has been the preferred material used for blade cleaning due to its toughness, resiliency and wear resistant properties. This blade material requires a small amount of solid (dry) lubrication on its edge, which contacts the surface to be cleaned, to reduce drag and prevent bonding of the interacting surfaces. Zinc stearate, Teflon.TM., Kynar.TM. and other dry lubricants have been used in blade cleaning in prior art. Untransferred toner "fines"; i.e., fine particles, provide lubrication to the blade during normal printing operations.
The cleaning method which is most used in current practice for the detone roller is that of a scraper blade made out of steel or phosphorus bronze as shown in one of the brush cleaner configurations in FIG. 3.
In the above applications, dusting inside the cleaner is particularly high during cleaning cycles where high levels of toner mass laydown are on the surfaces to be cleaned. Dusting emanates from the interface between the surface contaminated with charged toner particles and the blade edge. Containment of air borne toner particles is highly desirable in order to minimize the likelihood of leaks that will generate machine contamination. To prevent dusting from leaking out of the blade cleaner housing, the cleaner requires good overall sealing. Foam or brush seals, 3, at the front and back ends of the blade and an upstream sealing blade, 4, are among the methods used to prevent dust from leaking out. These sealing components are shown in FIGS. 1 and 2.
When the scraper blade is made out of steel, it usually has residual magnetism. This residual magnetism on the blade material causes magnetized carrier particles to be attracted to the blade edge. Magnetized carrier particles will be attracted to a ferromagnetic blade, even if it has no residual magnetism. A metallic blade will also form an extremely small nip which may result in higher wear and heat, especially when magnetized particles are trapped at its edge, with the consequent degradation in cleaning performance. The above method, using a magnetic stainless steel blade, when loaded with magnetic carrier particles will become ineffective as a cleaner quite rapidly.
Metallic blades have also been shown to reduce the drag on the surface to be cleaned thus requiring less lubrication than the polyurethane blades.
Metallic blades have shown comparable or higher expected life than polyurethane blades in the absence of carrier particles, but they have not been used to clean photosensitive or scratch-sensitive surfaces due to higher wear on these surfaces. Furthermore, when metallic blades are used, the surfaces to be cleaned require special surface treatments (Martin hard coats, chromium plating) to increase their wear resistance. These special surface treatments increase the cost of the parts. Polyurethane blades do not require such special surface treatments.
Carrier particles can also affect the performance of polyurethane blades if trapped in front of the cleaning edge due to excessive wear of the cleaning surface. In general, polyurethane blades have shown longer lives than steel blades in the presence of carrier particles.
Other types of contamination that can quickly degrade the cleaning blade performance, irrespective of the blade material, are paper dust and paper fibers and lint. As these contaminants are fed to the blade edge, they will build up under the edge and will weaken the sealing contact that the blade edge makes with the surface to be cleaned. The end result is cleaning failure in the form of toner bands or streaks.